Fiber and Cholesterol: Is There a Link? - Healthline

When you think of cholesterol-lowering foods, Cheerios or oatmeal may pop into your mind. Both boast the signature red heart on the packaging, along with the phrase "can help lower cholesterol as part of a heart-healthy diet."

Both products can sport this claim because of the fiber content of oats. Research indicates that eating a fiber-rich diet can lower cholesterol levels and therefore support heart health (1).

Here's what you need to know about dietary fiber and cholesterol levels.

Cholesterol is a waxy, fatlike substance that your liver naturally produces. Your body uses cholesterol to maintain the structure of cell membranes and to make vitamin D and hormones such as cortisol, estrogen, and testosterone (2).

Cholesterol doesn't travel well through your blood, because fat and water don't mix. So your liver produces substances called lipoproteins to transport cholesterol and triglycerides — a type of fat — in your bloodstream (2).

There are two main forms of cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL) (2).

LDL, also known as "bad" cholesterol, acts as a major transporter of cholesterol. Inflammation can oxidize LDL particles. These particles then become unstable and harmful, especially if there are a lot of them in your bloodstream.

High levels of LDL can harden arteries, lead to blockages, and increase the risk of heart disease. According to the Centers for Disease Control and Prevention (CDC), LDL levels should be less than 100 mg/dL (2, 3).

HDL is known as "good cholesterol" because it transports excess cholesterol from your blood back to your liver to be eliminated. According to the CDC, HDL levels should be above 60 mg/dL (2, 3).

The total amount of cholesterol in your blood is referred to as your total cholesterol. It is determined by your HDL, LDL, and triglycerides. Total cholesterol should be less than 200 mg/dL (3).

Eating fiber lowers cholesterol by lowering the amount of LDL cholesterol that is absorbed into your bloodstream.

Summary

Cholesterol is a vital substance produced by your body, but high levels of LDL ("bad") cholesterol are a risk factor for heart disease. Eating fiber may lower cholesterol by lowering the amount of LDL cholesterol in your blood.

Fiber refers to nondigestible carbohydrates — those that aren't broken down and absorbed in your digestive tract for energy.

Eating fiber, specifically soluble fiber, can lower LDL cholesterol levels.

Soluble fiber forms a gel-like substance in your intestines, slowing down digestion. It also traps cholesterol and prevents your body from reabsorbing it into your bloodstream. The trapped cholesterol is then excreted from your body in stool (1, 4).

In addition, bacteria living in your large intestine ferment, or feed on, soluble fiber.

This fermentation not only helps create a healthy gut that promotes the excretion of cholesterol but also produces short-chain fatty acids (SCFAs). Absorption of SCFAs decreases cholesterol synthesis in your liver, which also lowers blood cholesterol (4).

However, insoluble fiber does not lower cholesterol like soluble fiber does. Insoluble fibers don't form a gel and resist fermentation by gut bacteria. Instead, they add bulk to the stool, speed up digestion, and contribute to health in other ways (1).

How effective is soluble fiber at lowering cholesterol?

The 2020–2025 Dietary Guidelines for Americans advise that women should generally consume 25–28 grams of fiber per day and men should aim for 31–34 grams of fiber. That's about 14 grams of fiber for every 1,000 calories consumed (5).

For most Americans, the range of 25–35 grams of fiber per day would be considered increased consumption, with soluble fiber composing at least 6 grams of that amount (1).

Regular consumption of soluble fiber is associated with a 5–10% reduction in total cholesterol and LDL cholesterol levels (6).

But some food sources of soluble fiber may be more effective at lowering cholesterol than others. Read on to learn about some of these.

Summary

Soluble is effective at lowering total and LDL cholesterol levels by decreasing the synthesis of cholesterol in the body and by helping to increase excretion. Insoluble fiber does not have that same effect.

Here are 5 foods high in soluble fiber that may support healthy cholesterol levels.

1. Oats

Oats reign supreme among cholesterol-lowering foods. Oats are high in a type of soluble fiber called beta-glucan (7).

Several studies since the early 2000s have shown that daily doses of at least 3 grams and up to 5.6 grams of beta-glucan can reduce total and LDL cholesterol levels in people with either normal or high cholesterol (7).

A study including 80 participants with mildly elevated cholesterol levels found that consuming 70 grams of oats (just under 1 cup) — which contribute 3 grams of beta-glucan — daily for 4 weeks lowered total cholesterol by 8.1% and LDL cholesterol by 11.6% (8).

The reduction was significant in comparison with the control group (8).

Summary

Oats are high in a soluble fiber called beta-glucan, and eating about 1 cup of oats per day may help lower LDL cholesterol by about 11%.

2. Legumes

Legumes, including beans, peas, and lentils, are also high in soluble fiber. Below are the amounts of fiber in 1/2 cup of several types of cooked beans (9):

An analysis of data from 10 randomized clinical trials with 268 total participants evaluated the effects of non-soy legumes on cholesterol.

Results showed that consuming a legume-rich diet for a minimum of 3 weeks prompted an almost 12-point drop in total cholesterol levels and an 8-point drop in LDL levels (9).

Another study in 31 people with type 2 diabetes found that following a heart-healthy diet and replacing 2 servings of red meat — which does not contain fiber — with legumes 3 days a week for 8 weeks significantly lowered LDL levels as compared with a heart-healthy diet alone (10).

Summary

Legumes such as beans and lentils can help lower total and LDL cholesterol levels, especially as part of a heart-healthy diet.

3. Apples

Apples contain a soluble fiber called pectin. The European Food Safety Authority advises that about 6 grams of pectin daily has been reported to lower blood cholesterol levels (11).

Researchers in a small study with 40 participants investigated the effect of eating two apples per day, which contribute about 3.7 grams of pectin, compared with apple juice, which is stripped of the fibrous pectin content but contributes the same amount of sugar.

After 8 weeks of apple consumption, total and LDL cholesterol levels decreased (11).

Summary

Apples contain a soluble fiber called pectin and may contribute to reducing cholesterol levels, but more research is needed to understand the fruit's full effects on cholesterol.

4. Avocados

Avocados are a good source of fiber and healthy monounsaturated fats. One whole avocado provides around 4.7 grams of fiber, 1.4 grams of which are soluble (12).

A randomized controlled trial found that consuming one avocado a day as part of a healthy diet had beneficial effects on LDL cholesterol levels as compared with other sources of fat (13).

These benefits were primarily attributed to avocados' fat, fiber, and antioxidant content (13).

Summary

A whole avocado contains almost 5 grams of fiber. In addition to providing antioxidants and healthy fat, avocados appear to support healthy cholesterol levels.

5. Flaxseed

Flaxseed is another good source of soluble fiber and healthy fats. The relationship between flaxseed and blood cholesterol is well established.

An older review of 28 studies published between 1990 and 2008 found that whole flaxseed consumption — but not flaxseed oil consumption — reduced total and LDL cholesterol levels, particularly in postmenopausal people and those with high cholesterol (14).

Another older study found that flaxseed fiber powder consumed as a drink or baked into breads and eaten three times a day before meals reduced both total and LDL cholesterol levels, with the drink having a greater effect (15).

A recent analysis of 31 randomized controlled trials on flaxseed's effect on cholesterol found that whole flaxseed consumption consistently reduced triglyceride, LDL, and total cholesterol levels (16).

These benefits were most pronounced with a flaxseed consumption around 3 tablespoons (30 grams) or less per day (16).

Summary

Eating flaxseed has been shown to lower cholesterol levels, but flaxseed oil doesn't seem to offer the same cholesterol-lowering benefits.

While fiber supplements may help you reach the recommended 25–35 grams of fiber per day, they cannot take the place of eating a balanced diet that includes fiber-rich foods.

If you're looking for a soluble fiber to help lower cholesterol, psyllium supplements have the most research supporting their use for that purpose. More than 24 clinical trials have investigated the impact of psyllium on cholesterol, with daily doses of 6–15 grams.

Studies indicate that psyllium supplements may lower LDL cholesterol by 6–24% and total cholesterol by 2–20%, with the greatest benefits seen in people who have high cholesterol (17).

Other studies show that psyllium can be paired with statins — a class of cholesterol-lowering medications — to support further reductions in cholesterol (18).

Methylcellulose is another soluble fiber supplement, but it's not as well researched as psyllium (18).

Talk with a healthcare professional before adding fiber supplements to your routine, especially if you are taking a statin.

Summary

Eating whole foods with soluble fiber is the best dietary way to help lower cholesterol, but research does support the use of psyllium supplements. Consult a healthcare professional before starting a new supplement.

The following dietary and lifestyle factors may also help lower cholesterol:

• Exercise. Regular physical activity has been shown to increase HDL levels, which may offset some increases in LDL and triglycerides. Aim to get 30 minutes of exercise 5 times per week — ideally higher intensity aerobic exercise paired with resistance training (19).
• Lower saturated fat intake. Saturated fat is found primarily in animal products such as red meat and dairy. Replacing saturated fats with other fats or whole grains may lower your risk of cardiovascular events and improve blood cholesterol levels (20, 21).
• Stress management. One study found that psychological stress, such as stress from work, is a risk factor for increasing triglycerides and LDL and lowering HDL. The study also found physical activity to be protective against those effects (22).
• Loss of excess weight. Research shows that losing 5–10% of body weight may significantly improve cholesterol levels for those with high cholesterol who also have a higher body mass index (23).

Summary

In addition to consuming soluble fiber, exercising (especially aerobic exercise), decreasing saturated fat intake, managing stress, and losing 5–10% of excess body weight may help reduce cholesterol levels.

Including more soluble fiber in your diet is a great way to help lower or support healthy cholesterol levels and protect against heart disease. About 90% of women and 97% of men aren't meeting the daily fiber recommendations (5).

Most fibrous foods, such as whole grains, fruits, vegetables, and legumes, contain a mixture of soluble and insoluble fiber (5).

If your goal is to lower your cholesterol levels, try to include foods rich in soluble fiber in your diet, decrease your saturated fat intake, and incorporate exercise.